WO2009070096A1

WO2009070096A1 - Improved paging in td scdma

Info

Publication number: WO2009070096A1
Application number: PCT/SE2008/051165
Authority: WO
Inventors: Jie Mao; Jiuhui Du; Jingyue Nie
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2007-11-26
Filing date: 2008-10-15
Publication date: 2009-06-04
Anticipated expiration: 2010-05-26
Also published as: CN101874422A

Abstract

The invention discloses a method (400) for use in a wireless system (100) of the TD SCDMA kind (405), according to which method there is (410) a first carrier frequency for MBSFN services and (415) a second carrier frequency for non MBSFN services. According to the invention, the MBSFN carrier frequency is made to include a possibility for a user (140) of the MBSFN carrier frequency to be notified of a paging message to the user.

Description

IMPROVED PAGING IN TD SCDMA

TECHNICAL FIELD

The present invention discloses a method and a device for improved paging in a cellular system of the TD SCDMA kind.

BACKGROUND

In cellular systems of the TD SCDMA kind, i.e. systems which use Time Division Synchronous Code Division Multiple Access, a separate carrier can be configured for so called MBMS services, Multicast and Broadcast Services. This solution is known as MBSFN, i.e. MBMS over a single carrier frequency.

As the name implies, MBMS will let users enjoy multimedia session via their user devices, the devices being cellular telephones, laptop computers etc. However, an MBSFN user who is occupied with a multimedia session will not be available for non-MBSFN services, such as, for example, incoming calls.

SUMMARY It is a purpose of the present invention to alleviate the above described disadvantage of TD SCDMA systems which are MBSFN enabled.

This purpose is achieved by the present invention in that it discloses a method for use in a wireless system of the TD SCDMA kind, in which system there is a first carrier for MBSFN services and a second carrier for non MBSFN services.

According to the method of the invention, the MBSFN carrier is made to include a possibility for a user of the MBSFN carrier to be notified of a paging message to the user. Thus, since, according to the invention, an MBSFN user who is busy in an MBMS multimedia session can be made aware that a non-MBMS service, such as, for example, an incoming call, is directed to him. Using this knowledge, the user can terminate or suspend the multimedia session, and respond to the non MBSFN service which has originated the paging message.

In one version of the invention, the possibility to be notified of a paging message comprises a paging channel on the MBSFN carrier, on which channel the user can receive paging messages.

In another version of the invention, this possibility comprises a paging indication channel on which the user can receive an indication to switch to the non MBSFN carrier to receive and reply to a paging message for said user.

These and other embodiments of the invention will be described in more detail below.

The invention also discloses a transceiver for use as a controlling node of an MBSFN enabled TD SCDMA system.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail in the following, with reference to the appended drawings, in which

Fig 1 shows an overview of a system in which the invention can be applied, and

Fig 2 shows prior art channels in TD SCDMA, and Fig 3 shows TD SCDMA channels according to the present invention, and Fig 4 shows a flow chart of a method of the present invention, and Fig 5 shows a block diagram of a transceiver of the present invention. DETAILED DESCRIPTION

Fig 1 shows a basic overview of a system 100 in which the present invention can be applied. As indicated in fig 1 , the system 100 is a cellular system with one cell 110 being shown in fig 1.

A cell such as the cell 110 can hold a number of users with user devices, UEs ("User Equipment"), with fig 1 showing two UEs, 130, 140. Examples of user devices are cellular telephones or laptop computers which are enabled to connect to the system 100.

The system 100 for which the invention is intended is a TD SCDMA system, i.e. a system which uses Time Division Synchronous Code Division Multiple Access. In addition to this principle, the system 100 is enabled for so called MBMS, Multicast and Broadcast Services. For each cell, the MBMS services can be provided on a single frequency, so called MBSFN, i.e. MBMS over a single frequency. Alternatively, the MBSFN frequency can cover more than one non-MBSFN cell, so that the MBSFN cell overlaps one or more non- MBSFN cell.

The use of MBSFN and non MBSFN services in the cell 110 is symbolically indicated in fig 1 by means of arrows to/from the NodeB 120. As indicated, separate carrier frequencies f1 and f2 respectively are used for the MBSFN and non MBSFN services.

In a TD SCDMA system, so called paging messages are transmitted via the NodeB of a cell to a user in the cell, on the frequency used for non MBSFN services, which means that a user who is in a multimedia session on the MBSFN frequency will not be reached y a paging message intended for him, unless the UE of the user can support operation on more than one carrier at a time, which is an unlikely scenario with contemporary UEs. Thus, a user who is the intended receiver of a paging message and who uses MBSFN services will not receive the paging message and will for that reason miss the service that originated the paging message, such as a telephone call.

According to the present invention, the MBSFN carrier frequency is made to include a possibility for a user of the MBSFN carrier frequency to be notified of a paging message to the user. Before this possibility is described in more detail, the present use of the MBSFN and non MBSFN carrier frequencies, i.e. f1 and f2 will be described with reference to fig 2:

As shown in fig 2, at present the MBSFN carrier is used for a number of channels, the following, as shown in fig 2, being examples of such channels:

• BCH, Broadcast Channel,

• MICH, MBMMS Indicator Channel,

• MTCH, MBMS Traffic Channel

As also shown in fig 2, the non MBMS carrier is also used for a number of channels, examples of such channels, as shown in fig 2, being:

• BCH, Broadcast Channel,

• PICH, Paging Indicator Channel,

• PCH, Paging Channel, • DPCH, Dedicated Physical Channel

According to the present invention, the MBSFN carrier is made to include a possibility for a user of the MBSFN carrier frequency to be notified of a paging message to the user. This possibility can be embodied a number of ways, two of which will be explained below. In a first embodiment, the MBSFN carrier is made to include a paging indication channel, which may be code divided or time divided with the other channels of the MBSFN channel of the system. This is shown in fig 2 as PICH, "Paging Indication Channel"

Suitably, the function of the paging indication channel of the present invention is that the identity of the UE which is being paged is "mapped" to one or more bits or symbols in the paging indication channel. When a specific UE is being paged, either the ID of that UE can appear on the channel, or there can be a special symbol, such as an "enable" bit accompanying the ID, which if it is enabled will tell the UE that it is being paged.

If a certain UE is being paged, the UE can act in a number of different ways: suitably, the UE will change to the non MBSFN carrier, receive the paging and reply to the page and initiate a session with the user or application from which the paging originated. When the session on the non MBSFN carrier is finished, the user may return to the MSFN session, and resume it or initiate a new one.

Thus, a UE which is paged can either suspend an ongoing MBMS session in order to switch over to the NMSFN channel, or a paged UE may terminate an ongoing MBMS session in order to switch over to the NMBSFB carrier in order to reply to the page and possibly initiate a session on the NMBSFN carrier.

Similarly, if the user or the application which caused the paging UE to originate for some reason rejects the reply of the paging or an accompanying service setup request, the UE may also change back to the MBSFN carrier and resume a suspended session or initiate a new one, if the previous one was terminated. Fig 3 shows a possible disposition of the MBSFN and non MBSFN carriers in a system of the invention: as can be seen in fig 3, the MBSFN carrier now comprises a paging indicator channel, PICH, or, alternatively, a paging channel, PCH, which have the function or functions described above., It is also possible for the MBSFN carrier to include both PICH and PCH.

If a PCH and/or PICH are configured in the MBSFN carrier, the UE can receive paging message in the MBSFN carrier and switch to the non-MBSFN carrier in order to send a paging response and initiate a session with the user or application from which the paging originated.

In one embodiment of the invention, the paging indication channel or paging channel of the invention is configured in the so called MBSFN special burst, the MS burst, which is a shorter timeslot than other timeslots, and can be used for carrying control information in MBSFN carrier.

Suitably, the first and second carriers overlap each other frequency-wise, and, as mentioned, the system configuration can also be such that the MBSFN frequency covers more than one non-MBSFN ceils. In this configuration, the MBSFN "cell" is then actually a cell that overlaps the non- MBSFN cells.

Fig 4 shows a schematic flow chart of a method of the invention. Steps which are options or alternatives are indicated with dashed lines in fig 4.

As has been explained previously, the method 400 is intended for use in a wireless system of the TD SCDMA kind, which is also indicated in step 405, and according to the method 400, there is, as shown in step 410 a first carrier frequency for MBSFN services and, step 415, a second carrier frequency for non MBSFN services. As indicated in step 420, the MBSFN carrier frequency is made to include a possibility for a user of the MBSFN carrier frequency to be notified of a paging message to the user.

In one embodiment, as shown in step 425, the "paging possibility" comprises a paging channel on the MBSFN carrier frequency, on which channel the user can receive paging messages.

In another embodiment, as indicated in step 430, the "paging possibility" comprises a paging indication channel on which the user can receive an indication to switch to the non MBSFN carrier to receive and reply to a paging message for said user. Step 435 shows that this indication in one embodiment is one or more bits or symbols on the paging indication channel.

As indicated in step 440, in one version of the invention, if the user receives a notification of a paging message, the user suspends an ongoing MBSFN session in order to use a non MBSFN service which has triggered the paging message. Step 445 shows that the user can also resume the MBSFN session after terminating the non MBSFN service.

As indicated in step 450, in one embodiment, the first and second carriers overlap each other frequency-wise.

Fig 5 shows a schematic block diagram of a transceiver 500 for use as a user terminal, a UE₁ in a system in which the invention is applied. As indicated in fig 5, the UE 500 comprises an antenna, shown as block 510, and will also comprise a receive part 520 and a transmit part 530. In addition, the UE 500 also comprises a control means 540 such as a micro processor, as well as a memory 550.

Since the major components of the UE 500 have been identified above both with respect to their function with and their reference numbers, they may in the following be referenced merely by their reference numbers, e.g. "the means 510", instead of "the antenna 510".

As will have emerged from the description above, the user terminal 500 is intended for use in a wireless system of the TD SCDMA kind, and the user terminal 500 uses the 510, 520 530 for operating on a first carrier frequency for MBSFN services or on a second carrier frequency for non MBSFN services. In addition, the user terminal is equipped with means 520, 540, 550 for detecting a notification of a paging message on the MBSFN carrier frequency.

In one embodiment, the user terminal 500 uses the means 510, 520, 540, 550 for detecting a paging channel on the MBSFN carrier frequency, on which channel the user terminal can receive paging messages.

Also, in one embodiment, the user terminal 500 uses the means 510, 520, 540, 550 for detecting a paging indication channel on which the user terminal can receive an indication to switch to the non MBSFN carrier in order to receive and reply to a paging message for the user terminal. Suitably, in the user terminal 500 the "switching indication" is one or more bits or symbols on the paging indication channel.

In one embodiment, the user terminal 500 uses the means 510, 520, 530, 540, 550 for suspending an ongoing MBSFN session in order to use a non MBSFN service which has triggered the paging message, if the user terminal receives a notification of a paging message. Also, in one embodiment, the user terminal 500 uses the means 540, 550, 520, 530 for resuming the MBSFN session after terminating the non MBSFN service.

The invention is not limited to the examples of embodiments described above and shown in the drawings, but may be freely varied within the scope of the appended claims.

Claims

1. A method (400) for use in a wireless system (100) of the TD SCDMA kind (405), according to which method there is a first carrier frequency (410) for MBSFN services and a second carrier frequency (415) for non MBSFN services, the method being characterized in that the MBSFN carrier frequency (420) is made to include a possibility for a user (140) of the MBSFN carrier frequency to be notified of a paging message to the user.

2. The method (400) of claim 1 , according to which said possibility (425) comprises a paging channel on the MBSFN carrier frequency, on which channel the user can receive paging messages.

3. The method (400) of claim 1 or 2, according to which said possibility (430) comprises a paging indication channel on which the user (140) can receive an indication to switch to the non MBSFN carrier to receive and reply to a paging message for said user.

4. The method (400) of claim 3, according to which said indication (435) is one or more bits or symbols on the paging indication channel.

5. The method (400) of any of clams 1-4, according to which, if said user (140) receives a notification of a paging message, the user suspends (440) an ongoing MBSFN session in order to use a non MBSFN service which has triggered the paging message.

6. The method (400) of claim 5, according to which the user (140) resumes (445) the MBSFN session after terminating the non MBSFN service.

7. The method (400) of any of the previous claims, according to which said first and second carriers overlap (450) each other frequency-wise.

8. A user terminal (500) for use in a wireless system (100) of the TD SCDMA kind (405), the user terminal (500) being equipped with means (510, 520 530) for operating on a first carrier frequency for MBSFN services or on a second carrier frequency for non MBSFN services, the user terminal being characterized in that it is equipped with means (520, 540, 550) for detecting a notification of a paging message on the MBSFN carrier frequency.

9. The user terminal (500) of claim 8, which is equipped with means (510, 520, 540, 550) for detecting a paging channel on the MBSFN carrier frequency, on which channel the user terminal can receive paging messages.

10. The user terminal (500) of claim 8 or 9, which is equipped with means (510, 520, 540, 550) for detecting a paging indication channel on which the user terminal (500) can receive an indication to switch to the non MBSFN carrier in order to receive and reply to a paging message for the user terminal.

11. The user terminal (500) of claim 10, in which the indication is one or more bits or symbols on the paging indication channel.

12. The user terminal (500) of any of clams 8-11 , which is equipped with means (510, 520, 530, 540, 550) for, if the user terminal receives a notification of a paging message, suspending an ongoing MBSFN session in order to use a non MBSFN service which has triggered the paging message.

13. The user terminal (500) of claim 12, which is equipped with means (540, 550, 520, 530) for resuming the MBSFN session after terminating the non MBSFN service.